QD type hook bridge crane is 5t. The brake of the lifting mechanism is TJZ-200 short-stroke AC electromagnet block brake. TJZ-200 short-stroke AC electromagnet block brake and MZD1-200 electromagnet are specified in the manufacturer's instruction manual and technical data:
(1)Adjustment gap (mm) normal value/maximum value=0.3/0.5;(2)The main spring assembly length error does not exceed ±lmm,(3)Braking wheel diameter200mm, the temperature should not exceed200℃;(4)Repeated short-time working system, the power-on continuity rate should not exceed 300 times per hour under the condition that the power continuity rate does not exceed 40%. Reason:11, MZDl-200 electromagnets are inherently deficient in electricalPoor performance, energy consuming, and unsafe. This is the fundamental reason why this type of electromagnet often burns the coil. 2. After inspection, the crane is often in an overloaded state, and the actual lifting capacity is 1.2 to 1.6 times the rated lifting capacity, that is, 6 to 8t. In this way, the brake must reliably support 1.2×1.25~1.6×1.25 times of the rated lifting weight, that is, 7.5~10t. Correspondingly, the main spring must be adjusted to further compress and deform, increasing the braking torque, causing the brake lever (push rod) stroke to exceed the normal allowable value (3.8mm), the rotation angle of the electromagnet armature exceeds the rated rotation angle by 5.5°. The result is:1)Because the armature angle increases, the closed magnetic circuit of the electromagnet grows at a certain distance in the air gap, the magnetic resistance increases, the magnetic flux decreases, the self-inductance L decreases, and the inductive reactance sourcevalue="125" unitname="℃">125℃, the insulation performance is damaged, and due to frequent operation, the temperature continues to remain around 125C℃. 2)The attraction force of the electromagnet's static iron core weakens due to the increase in the armature's circular angle, and the armature's rotation angle acceleration decreases.The time of the armature rotation process is extended (that is, the time from the armature starting to rotate to the time of suction is extended). During this process, the coil current intensity is large (variable), and the temperature is both high and lasts longer than normal, resulting in insulation damage. 3)Due to overload, the braking torque of the main spring is no longer enough to brake the vehicle during the lifting process. In order to brake the car, the operator uses the side-pull reverse braking method. That is, when the cargo slowly descends and drives the motor rotor to rotate in the downward direction, the operator moves the handle of the cam controller from zero to the up gear. The electromagnetic torque of the motor and the rotation direction of the rotor are reversed, becoming braking torque to prevent the cargo from falling. At this time, the brake coil changes from the power-off state to the energization state. Due to busy tasks and neglect of safety operating procedures, overloaded operations are frequent. During the operation, the position of the cargo in space needs to be adjusted, which causes the above method to be used for braking more often. The number of times the raft is energized exceeds the normal lifting capacity. This is also a reason why the coil is overheated for a long time and cannot be heated in time. 3. Coil quality issues. The coil winding quality is poor, there is no interlayer insulation, the insulation strength is reduced, and the heat resistance is reduced. Sometimes the water is even put on before the water is dry. Under normal load, the characteristics of the coil no longer meet the needs of normal working conditions, not to mention that if it is replaced under overload conditions, it will inevitably burn out more easily.
QD type hook bridge crane is 5t. The brake of the lifting mechanism is TJZ-200 short-stroke AC electromagnet block brake. TJZ-200 short-stroke AC electromagnet block brake and MZD1-200 electromagnet are specified in the manufacturer's instruction manual and technical data:
(1)Adjustment gap (mm) normal value/maximum value=0.3/0.5;(2)The main spring assembly length error does not exceed ±lmm,(3)Braking wheel diameter200mm, the temperature should not exceed200℃;(4)Repeated short-time working system, the power-on continuity rate should not exceed 300 times per hour under the condition that the power continuity rate does not exceed 40%. Reason:11, MZDl-200 electromagnets are inherently deficient in electricalPoor performance, energy consuming, and unsafe. This is the fundamental reason why this type of electromagnet often burns the coil. 2. After inspection, the crane is often in an overloaded state, and the actual lifting capacity is 1.2 to 1.6 times the rated lifting capacity, that is, 6 to 8t. In this way, the brake must reliably support 1.2×1.25~1.6×1.25 times of the rated lifting weight, that is, 7.5~10t. Correspondingly, the main spring must be adjusted to further compress and deform, increasing the braking torque, causing the brake lever (push rod) stroke to exceed the normal allowable value (3.8mm), the rotation angle of the electromagnet armature exceeds the rated rotation angle by 5.5°. The result is:1)Because the armature angle increases, the closed magnetic circuit of the electromagnet grows at a certain distance in the air gap, the magnetic resistance increases, the magnetic flux decreases, the self-inductance L decreases, and the inductive reactance sourcevalue="125" unitname="℃">125℃, the insulation performance is damaged, and due to frequent operation, the temperature continues to remain around 125C℃. 2)The attraction force of the electromagnet's static iron core weakens due to the increase in the armature's circular angle, and the armature's rotation angle acceleration decreases.The time of the armature rotation process is extended (that is, the time from the armature starting to rotate to the time of suction is extended). During this process, the coil current intensity is large (variable), and the temperature is both high and lasts longer than normal, resulting in insulation damage. 3)Due to overload, the braking torque of the main spring is no longer enough to brake the vehicle during the lifting process. In order to brake the car, the operator uses the side-pull reverse braking method. That is, when the cargo slowly descends and drives the motor rotor to rotate in the downward direction, the operator moves the handle of the cam controller from zero to the up gear. The electromagnetic torque of the motor and the rotation direction of the rotor are reversed, becoming braking torque to prevent the cargo from falling. At this time, the brake coil changes from the power-off state to the energization state. Due to busy tasks and neglect of safety operating procedures, overloaded operations are frequent. During the operation, the position of the cargo in space needs to be adjusted, which causes the above method to be used for braking more often. The number of times the raft is energized exceeds the normal lifting capacity. This is also a reason why the coil is overheated for a long time and cannot be heated in time. 3. Coil quality issues. The coil winding quality is poor, there is no interlayer insulation, the insulation strength is reduced, and the heat resistance is reduced. Sometimes the water is even put on before the water is dry. Under normal load, the characteristics of the coil no longer meet the needs of normal working conditions, not to mention that if it is replaced under overload conditions, it will inevitably burn out more easily.
QD type hook bridge crane is 5t. The brake of the lifting mechanism is TJZ-200 short-stroke AC electromagnet block brake. TJZ-200 short-stroke AC electromagnet block brake and MZD1-200 electromagnet are specified in the manufacturer's instruction manual and technical data:
(1)Adjustment gap (mm) normal value/maximum value=0.3/0.5;(2)The main spring assembly length error does not exceed ±lmm,(3)Braking wheel diameter200mm, the temperature should not exceed200℃;(4)Repeated short-time working system, the power-on continuity rate should not exceed 300 times per hour under the condition that the power continuity rate does not exceed 40%. Reason:11, MZDl-200 electromagnets are inherently deficient in electricalPoor performance, energy consuming, and unsafe. This is the fundamental reason why this type of electromagnet often burns the coil. 2. After inspection, the crane is often in an overloaded state, and the actual lifting capacity is 1.2 to 1.6 times the rated lifting capacity, that is, 6 to 8t. In this way, the brake must reliably support 1.2×1.25~1.6×1.25 times of the rated lifting weight, that is, 7.5~10t. Correspondingly, the main spring must be adjusted to further compress and deform, increasing the braking torque, causing the brake lever (push rod) stroke to exceed the normal allowable value (3.8mm), the rotation angle of the electromagnet armature exceeds the rated rotation angle by 5.5°. The result is:1)Because the armature angle increases, the closed magnetic circuit of the electromagnet grows at a certain distance in the air gap, the magnetic resistance increases, the magnetic flux decreases, the self-inductance L decreases, and the inductive reactance sourcevalue="125" unitname="℃">125℃, the insulation performance is damaged, and due to frequent operation, the temperature continues to remain around 125C℃. 2)The attraction force of the electromagnet's static iron core weakens due to the increase in the armature's circular angle, and the armature's rotation angle acceleration decreases.The time of the armature rotation process is extended (that is, the time from the armature starting to rotate to the time of suction is extended). During this process, the coil current intensity is large (variable), and the temperature is both high and lasts longer than normal, resulting in insulation damage. 3)Due to overload, the braking torque of the main spring is no longer enough to brake the vehicle during the lifting process. In order to brake the car, the operator uses the side-pull reverse braking method. That is, when the cargo slowly descends and drives the motor rotor to rotate in the downward direction, the operator moves the handle of the cam controller from zero to the up gear. The electromagnetic torque of the motor and the rotation direction of the rotor are reversed, becoming braking torque to prevent the cargo from falling. At this time, the brake coil changes from the power-off state to the energization state. Due to busy tasks and neglect of safety operating procedures, overloaded operations are frequent. During the operation, the position of the cargo in space needs to be adjusted, which causes the above method to be used for braking more often. The number of times the raft is energized exceeds the normal lifting capacity. This is also a reason why the coil is overheated for a long time and cannot be heated in time. 3. Coil quality issues. The coil winding quality is poor, there is no interlayer insulation, the insulation strength is reduced, and the heat resistance is reduced. Sometimes the water is even put on before the water is dry. Under normal load, the characteristics of the coil no longer meet the needs of normal working conditions, not to mention that if it is replaced under overload conditions, it will inevitably burn out more easily.
